package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisData;
import com.hmdp.utils.SystemConstants;
import org.springframework.data.geo.Distance;
import org.springframework.data.geo.GeoResult;
import org.springframework.data.geo.GeoResults;
import org.springframework.data.redis.connection.RedisGeoCommands;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.domain.geo.GeoReference;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    @Resource
    private RedisTemplate redisTemplate;

    /**
     * 根据id查询店铺信息
     * @param id 店铺id
     * @return
     */
    @Override
    public Result queryById(Long id) {
        //缓存穿透
        Shop shop = queryWithPassThough(id);

        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);
        //逻辑过期解决缓存击穿
        //Shop shop = queryWithLogicalExpire(id);
        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        return Result.ok(shop);
    }

    private Shop queryWithMutex(Long id) {
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = (String) redisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.缓存命中，直接返回商铺信息
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //3.判断命中是否为空
        if (shopJson != null) {
            return null;
        }
        //4.缓存重建
        //4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2判断是否获取锁成功
            while (!isLock) {
                //4.3失败 休眠并重试
                Thread.sleep(50);
            }
            //2.判断是否存在
            if (StrUtil.isNotBlank(shopJson)) {
                //3.缓存命中，直接返回商铺信息
                Shop shop = JSONUtil.toBean(shopJson, Shop.class);
                return shop;
            }
            //判断命中是否为空
            if (shopJson != null) {
                return null;
            }
            //4.4成功 根据id查询数据库
            Shop shop = getById(id);
            //模拟重建的延时
            Thread.sleep(200);
            //5.不存在，返回错误
            if (shop == null) {
                //6.将空值写入redis
                redisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                //返回错误信息
                return null;
            }
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放互斥锁
            unLock(lockKey);
        }
        //8.存在 返回数据
        return null;
    }

    //创建一个线程池
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //逻辑过期解决缓存击穿
    public Shop queryWithLogicalExpire(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = (String) redisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            //3.直接返回商铺信息
            return null;
        }
        //4.命中，需要把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())){
            //5.1未过期，直接返回店铺信息
            return shop;
        }
        //5.2已过期，需要缓存重建
        //6.重建缓存
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Boolean isLock = tryLock(lockKey);
        //6.2判断是否获取成功
        if (isLock) {
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //重建缓存
                    this.saveShopToRedis(id, 20L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4返回过期的商铺信息
        return shop;
    }

    public Shop queryWithPassThough(Long id){
        String key = CACHE_SHOP_KEY + id;
        //1.从redis中查询商铺缓存
        String shopJson = (String) redisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.缓存命中，直接返回商铺信息
            Shop shop = JSONUtil.toBean(shopJson, Shop.class);
            return shop;
        }
        //判断命中是否为空
        if (shopJson != null) {
            return null;
        }
        //4.缓存未命中，查询数据库
        Shop shop = getById(id);
        //5.判断数据库中是否存在
        if (shop == null) {
            //6.不存在，将空值写入redis
            redisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //7.存在，将商铺数据写入redis，返回商铺信息
        redisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop),CACHE_SHOP_TTL, TimeUnit.MINUTES);
        return shop;
    }

    //创建锁
    private Boolean tryLock(String key) {
        Boolean flag = redisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private void unLock(String key) {
        redisTemplate.delete(key);
    }

    //向店铺写入数据 设置逻辑过期时间
    public void saveShopToRedis(Long id, Long expireSeconds) throws InterruptedException {
        //1.查询商铺数据
        Shop shop = getById(id);
        Thread.sleep(200);
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入Redis
        redisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if(id == null){
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.删除Redis缓存
        redisTemplate.delete(CACHE_SHOP_KEY + id);
        return Result.ok();
    }

    @Override
    public Result queryShopByType(Integer typeId, Integer current, Double x, Double y) {
        //1.判断是否需要根据坐标查询
        if (x == null || y == null) {
            //根据类型分页查询
            Page<Shop> page = query()
                    .eq("type_id", typeId)
                    .page(new Page<>(current, SystemConstants.DEFAULT_PAGE_SIZE));
            //返回数据
            return Result.ok(page.getRecords());
        }
        //2.计算分页参数
        int from = (current - 1) * SystemConstants.DEFAULT_PAGE_SIZE;
        int end = current * SystemConstants.DEFAULT_PAGE_SIZE;

        //3.查询redis、按照距离排序、分页。结果：shopId、distance
        String key = SHOP_GEO_KEY + typeId;
        GeoResults<RedisGeoCommands.GeoLocation<String>> results = redisTemplate.opsForGeo()
                .search(
                        key,
                        GeoReference.fromCoordinate(x, y),
                        new Distance(5000),
                        RedisGeoCommands.GeoSearchCommandArgs.newGeoSearchArgs().includeDistance().limit(end)
                );
        //4.解析出id
        if (results == null) {
            return Result.ok(Collections.emptyList());
        }
        List<GeoResult<RedisGeoCommands.GeoLocation<String>>> list = results.getContent();
        if (list.size() <= from) {
            //没有下一页了，结束
            return Result.ok(Collections.emptyList());
        }
        //4.1截取from 到 end
        List<Long> ids = new ArrayList<>(list.size());
        Map<String, Distance> distanceMap = new HashMap<>(list.size());
        list.stream().skip(from).forEach(result -> {
            String shopIdStr = result.getContent().getName();
            ids.add(Long.valueOf(shopIdStr));
            //4.2 获取距离
            Distance distance = result.getDistance();
            distanceMap.put(shopIdStr,distance);
        });
        //5.根据id查询shop
        String idStr = StrUtil.join(",", ids);
        List<Shop> shops = query().in("id", ids).last("ORDER BY FIELD(id," + idStr + ")").list();
        for (Shop shop : shops) {
            shop.setDistance(distanceMap.get(shop.getId().toString()).getValue());
        }
        //6.返回
        return Result.ok(shops);
    }
}
